Wire bonding apparatus, record medium storing bonding control program, and bonding method

ABSTRACT

A wire bonding apparatus including a bonding control section provided with an electrical non-bonding detector, an optical non-bonding detector, and an optical shape detector, which are for detecting non-bonding between a first bonding point and a bonding wire; and when non-bonding is detected by the electrical non-bonding detector and non-bonding is also detected by the optical non-bonding detector, then the tip end of the bonding wire is reformed by, based on the shape of the tip end of the bonding wire detected by the optical shape detector, a ball formation device into a ball of a prescribed shape, and rebonding is performed at the first bonding point.

This application is a divisional of Ser. No. 11/645,943, filed Dec. 17,2006, now U.S. Pat. No. 7,686,204.

BACKGROUND OF THE INVENTION

The present invention relates to a wire bonding apparatus, a bondingcontrol program, and a bonding method for performing recovery processingafter detecting non-bonding.

One of the assembly processes for semiconductors such as ICs (integratedcircuits) is a wire bonding process for connecting between asemiconductor chip and a lead frame with wires.

In a typical wire bonding process, as seen from FIG. 15, pads 3 (firstbonding points) of a semiconductor chip 2 and leads 4 (second bondingpoints) of a lead frame 15, both on a work 14, are connected by wires12. FIG. 12 shows a structure of a conventional wire bonding apparatus,FIG. 13 is a flowchart of the bonding steps taken in this wire bondingapparatus, and FIG. 14 shows the bonding steps in conventional bondingprocess. This conventional wire bonding apparatus and process will bedescribed below with reference to FIGS. 12 to 15.

In the wire bonding apparatus 100, as shown in FIG. 12, a bonding head19 is set up on an XY table 20; and a bonding arm 13, moved in a Zdirection by a motor, is provided on the bonding head 19; and inaddition, a capillary 16 is attached to the tip end of the bonding arm13.

The XY table 20 and the bonding head 19 make a moving mechanism 18. Themoving mechanism 18, by the XY table 20, moves the bonding head 19 toany position in a horizontal plane (in the XY plane), and, by moving thebonding arm 13 attached thereto in the Z direction, the capillary 16 atthe tip end of the bonding arm 13 is moved freely in the XYZ directions.A wire 12 is made to pass through the tip end of the bonding arm 13. Thewire 12 is wound on a spool 11. To the wire 12 wound on the spool 11, anelectrical conduction state acquisition device 22 is connected so as toacquire the electrical conduction state between the wire 12 and the work14 by applying to and measuring electric current or electric voltagebetween the wire 12 and the work 14. To the bonding head 19, a clamper17, that moves in the Z direction together with the capillary 16 andsecures the wire 12, is attached so that it can freely open and close.To the bonding head 19, moreover, a position detection camera 128 forverifying the position of the semiconductor chip 2 is attached. Also, inthe vicinity of the tip end of the wire 12, a ball formation device 26(called electric torch or electric flame off probe) is attached foreffecting electrical discharges between the wire 12 and forming a ball 5at the tip end of the wire 12. The position detection camera 128 isconnected to a position detection camera interface 140, the electricalconduction state acquisition device 22 is connected to an electricalconduction state acquisition device interface 42, the moving mechanism18 is connected to a moving mechanism interface 44, and the ballformation device 26 (electric torch) are connected to a ball formationdevice interface 46. Each interface is in turn connected via a data bus32 to a control section 30 within a computer 31 for controlling the wirebonding apparatus. To the data bus 32, furthermore, a memory unit 34 isconnected for storing control data. The above-described wire bondingapparatus is disclosed in, for instance, Japanese Patent ApplicationUnexamined Publication Disclosure No. 2003-163243.

The wire bonding apparatus 100 is controlled by the computer 31 andperforms wire bonding with the following steps.

-   -   (1) The tip end of a wire 12 is formed into a ball 5 by the ball        formation device 26, the position of the semiconductor chip 2 is        detected by the position detection camera 128, and the capillary        16 is moved over a pad 3 (first bonding point) by the moving        mechanism 18 (step S901 in FIG. 13, step (a) in FIG. 14).    -   (2) The capillary 16 is then caused to descend, and bonding is        performed on the pad 3 (first bonding point) (step S902 in FIG.        13, step (b) in FIG. 14). The ball 5 is pressure-bonded on the        pad 3 (first bonding point), so that a first bond portion 6        (pressure bonded ball) is formed.    -   (3) The moving mechanism 18 causes the capillary 16 to ascend        from the pad 3 (first bonding point) and then moves the        capillary 16 laterally (step S903 in FIG. 13, step (c) in FIG.        14).    -   (4) During the movement of the capillary 16, an electric current        is made to flow from the wire 12 to the work 14 by the        electrical conduction state acquisition device 22, and the        electrical conduction state at that time is acquired by the        electrical conduction state acquisition device 22. The acquired        data are input to the control section 30 via the electrical        conduction state acquisition device interface 42 (step S904 in        FIG. 13, step (c) in FIG. 14). When the bonding to the pad 3        (first bonding point) is successful and bonding has been        performed well, then an electric current is made to flow from        the wire 12 to the work 14 in step (c).    -   (5) In the case of non-bonding (in the case that wire 12 is not        bonded to the work 14), no first bond 6 is formed on the pad 3        (first bonding point), and the capillary 16 will ascend and move        with the wire 12 at the tip end of the capillary 16 not        connected to the pad 3 (first bonding point); as a result, no        current will flow from the wire 12 to the work 14. It is thereby        made possible to detect wire non-bonding. Acquired data on the        electrical conduction state between the wire 12 and the work 14        are processed in the electrical non-bonding detection step by        the control section 30, and whether non-bonding has occurred is        determined (step S905 in FIG. 13, step (c′) in FIG. 14) (see        Japanese Patent Application Unexamined Publication Disclosure        Nos. H2 (1990)-298874 and H7 (1995)-94545, for instance).    -   (6) When it is determined in the electrical non-bonding        detection step that non-bonding has occurred, the capillary 16        continues as before to move to a lead 4 (second bonding point),        bonding is performed at the lead 4 (second bonding point), and,        after causing the capillary 16 to ascend, the wire 12 is cut        (steps S906 to S908 in FIG. 13). No electrical conduction state        acquisition is, however, made for detecting a no-tail or lead        non-bonding at the lead 4 (second bonding point).    -   (7) When wire cutting is finished, error processing is effected        by a pad 3 (first bonding point) non-bonding signal, and the        wire bonding apparatus 100 is stopped (step S909 in FIG. 13).    -   (8) Meanwhile, after bonding to the pad 3 (first bonding point),        the moving mechanism 18 moves the capillary 16 to the lead 4        (second bonding point) and performs bonding at the lead 4        (second bonding point). If it is determined in the electrical        non-bonding detection step that the pad 3 is not non-bonding        (bonding on the pad 3 is successful), then when the capillary 16        is made to ascend thereafter, a current is made to flow from the        wire 12 to the work 14 by the electrical conduction state        acquisition device 22, and the electrical conduction state is        acquired by the electrical conduction state acquisition device        22. When bonding to the lead 4 (second bonding point) is        successful, and a tail wire 8 is formed properly at the tip end        of the capillary 16, a current is able to flow from the wire 12        to the work 14. Conversely, if the wire 12 is accidentally cut        while the capillary 16 is ascending, the current from the wire        12 to the work 14 will cease to flow. It is thus possible to        detect whether or not the tail wire 8 is a no-tail in which the        tail wire 8 fails to attain a prescribed length. Acquired data        are input to the control section 30 via the electrical        conduction state acquisition device interface 42 (steps S911 and        S912 in FIG. 13, step (d) in FIG. 14 to steps (e) and (e′)).    -   (9) After the bonding to the lead 4 (second bonding point), the        clamper 17 closes and ascends together with the capillary 16;        and, as a result, the wire 12 is cut above a second bond 7        (step (e) to (f)). After this wire cutting also, a current will        be made to flow from the wire 12 to the work 14 by the        electrical conduction state acquisition device 22, and the        electrical conduction state at that time will be acquired by the        electrical conduction state acquisition device 22 (steps S913        and S914 in FIG. 13).    -   (10) If the bonding to the lead 4 (second bonding point) is        successful and the cutting of the wire 12 is being properly        effected, then when the capillary 16 is ascending, the current        that was flowing from the wire 12 to the work 14 will have        ceased to flow (step (f) in FIG. 14). When the cutting of the        wire 12 is not being properly effected, on the other hand, as in        the case that the wire 12 has been peeled away from the work 14,        for example, the wire 12 will be electrically connected to the        work 14 through the first bond 6, as shown in FIG. 14( f), as a        result a current will flow. Moreover, when the current ceases to        flow prior to the closing and ascending of the clamper 17, and        no current is flowing even after the wire 12 is cut, even though        the second bond 7 will have been formed, it will be possible to        determine that there is a no-tail with the tail wire 8 not        attaining the prescribed length. Thus, by processing the data        output from the electrical conduction state acquisition device        22 in an electrical no-tail detection step in the computer 31,        it is possible to determine whether the electrical conduction        state after bonding to the lead 4 (second bonding point) is a        no-tail or a lead non-bonding condition (steps S915 and S917 in        FIG. 13) (see Japanese Patent Application Unexamined Publication        Disclosure Nos. H2 (1990)-298874 and H7 (1995)-94545, for        instance).    -   (11) When a no-tail or lead non-bonding is detected in the        electrical no-tail detection step, by a signal therefrom, the        wire bonding apparatus 100 performs error processing and stops        (see Japanese Patent Application Laid-Open Disclosure H6        (1994)-5651, for example).    -   (12) When bonding to the lead 4 (second bonding point) has        finished properly, the bonding cycle ends, and the capillary 16        is moved toward the next pad 3 (which is a next first bonding        point).

In the above description of the conventional art, wire non-bonding orno-tails are detected by processing signals from the electricalconduction state acquisition device 22 in the control section 30 of thecomputer 31 and, when it is determined thereby that a non-bonding orno-tail has occurred, then the wire bonding apparatus 100 is stopped.However, during a wire bonding process, various errors, in addition towhat is described above, occur, such as the ball not being properlyformed due to an electric discharge deficiency, when forming the ball 5at the tip end of the wire 12 by electric discharge. In such cases also,conventionally, the wire bonding apparatus is stopped when a flaw isdetected (see Japanese Patent Application Laid-Open Disclosure Nos. H6(1994)-5651 and H3 (1991)-17376). Also, in view of the fact that thereare cases where an error such as non-bonding or the like is caused whena ball 5 of the prescribed shape is not formed at the tip end of thecapillary 16, methods have been proposed in which the wire bondingapparatus is stopped or an anomaly alarm is effected after imaging theshape of the tip end of that wire and processing the resulting data (seeJapanese Patent Application Laid-Open Disclosure No. 2003-163243).

In the wire bonding apparatus 100 described in the above-referred art,despite the fact that various non-bonding detection device and methodsare provided, when an error such as non-bonding is detected, nothingmore is done besides stopping the wire bonding apparatus 100 or issuinga flaw alarm, and the apparatus does not process (correct) the errorcondition and continue bonding.

To the contrary, Japanese Patent Application Laid-Open Disclosure No. H6(1994)-5651, for example, discloses that when it is determined byelectrically detecting a discharge error that the tip end of the wire 12is not formed in a prescribed ball shape, abandoning bond is performedat an unnecessary portion of the material being bonded, a ball isreformed, and then bonding is continued. However, with this method,unnecessary wire remains at the abandoning bond position, giving rise tothe possibility of short-circuit, which is a problem.

Moreover, as to such errors as non-bonding in pad 3 (first bondingpoint) and lead 4 (second bonding point) and no-tail, since thesituation at the tip end of the wire 12 varies, a simple recoveryprocess such as the abandoning bond described above cannot be effected,and it will always be necessary to stop the whole bonding process andperform recovery process after an operator has verified the situation ofthe wire 12 and the like. Thus, it is not possible to recover from sucherrors and continue bonding.

BRIEF SUMMARY OF THE INVENTION

Accordingly, the object of the present invention is to provide a wirebonding apparatus, a bonding control program, and a bonding method inwhich, when a pad (first bonding point) non-bonding, lead (secondbonding point) non-bonding, no-tail, or discharge error or the likeoccurs, recovery processing is executed without stopping the wirebonding apparatus, continuing bonding actions.

The object of the present invention can be accomplished by a wirebonding apparatus that includes

-   -   a moving mechanism for moving, in XYZ directions, a capillary        having a wire inserted therethrough and executing bonding on a        work;    -   an electrical conduction state acquisition device for detecting        an electrical conduction state by allowing an electric current        to flow from the wire to the work;    -   a first means for taking an image of the work;    -   a light path device for conducting an elevation image of a        vicinity of a tip end of the capillary to the first means;    -   a ball formation device for forming a tip end of the wire into a        ball of a prescribed shape; and    -   a computer for controlling wire bonding between a first bonding        point and a second bonding point, the computer including        -   a second means for electrically detecting non-bonding            between the first bonding point and the wire by processing            electrical conduction state signals acquired by the            electrical conduction state acquisition device and            indicative of electrical conduction state between the first            bonding point and the wire,        -   a third means for optically detecting non-bonding between            the first bonding point and the wire by processing plane            images acquired by the first means,        -   a fourth means for detecting a shape of a tip end of the            wire by processing elevation images of the wire in the            vicinity of the tip end of the capillary acquired by the            first means via the light path device, and        -   a fifth means for, when non-bonding is detected by the            second means and non-bonding is detected by the third means,            reforming the tip end of the wire into a ball of prescribed            shape by the ball formation device, based on the tip end            shape of the wire detected by the fourth means, and            executing rebonding on the first bonding point.

The above-described wire bonding apparatus can further includes a sixthmeans for opening and closing a plurality of clampers, respectively, forgripping the wire; and the above-described computer can further includesa seventh means for, when non-bonding is detected by the second meansand non-bonding is detected by the third means and a condition of thewire, which is at the tip end of the capillary and detected by thefourth means, is not a prescribed condition, paying out the wire at thetip end of the capillary until the wire at the tip end of the capillaryattains a prescribed condition, by an up-and-down movement of thecapillary caused by the sixth means and moving mechanism, based on acondition of the wire at the tip end of the capillary detected by thefourth means.

The object of the present invention can be accomplished by a wirebonding apparatus which is characterized in that it includes

-   -   a moving mechanism for moving, in XYZ directions, a capillary        having a wire inserted therethrough and executing bonding on a        work;    -   an electrical conduction state acquisition device for detecting        an electrical conduction state by allowing an electric current        to flow from the wire to the work;    -   a first means for taking an image of the work;    -   a light path device for conducting an elevation image of a        vicinity of a tip end of the capillary to the first means;    -   a ball formation device for forming a tip end of the wire into a        ball of a prescribed shape;    -   a second means for opening and closing a plurality of clampers,        respectively, for gripping the wire; and    -   a computer for controlling wire bonding by cutting the wire        after bonding between a first bonding point and a second bonding        point, and this computer includes        -   a third means for detecting no-tail, in which a tail of the            wire fails to have a prescribed length, by processing            electrical conduction state signals acquired by the            electrical conduction state acquisition device, after            bonding to the second bonding point but prior to wire            cutting, and indicative of electrical conduction state            between a second bonding point and the wire,        -   a fourth means for detecting a shape of a tip end of the            wire by processing elevation images of the wire in the            vicinity of the tip end of the capillary acquired by the            first means via the light path device,        -   a fifth means for, when no-tail is detected by the third            means and an output is made from the fourth means to the            effect that a condition of the wire at the tip end of the            capillary is not a prescribed condition, paying out the wire            at the tip end of the capillary until the wire at the tip            end of the capillary attains a prescribed condition, by an            up-and-down movement of the capillary caused by the second            means and moving mechanism, based on a condition of the wire            at the tip end of the capillary detected by the fourth            means, and        -   a sixth means for reforming the tip end of the wire into a            ball of a prescribed shape by the ball formation device            based on the tip end shape of the wire detected by the            fourth means.

The object of the present invention can be accomplished by a wirebonding apparatus which is characterized in that it includes

-   -   a moving mechanism for moving, in XYZ directions, a capillary        having a wire inserted therethrough and executing bonding on a        work;    -   a first means for taking an image of the work;    -   a light path device for conducting an elevation image of a        vicinity of a tip end of the capillary to the first means;    -   a ball formation device for forming a tip end of the wire into a        ball of a prescribed shape by an electrical discharge between a        discharge electrode and the wire;    -   an electrical discharge state acquisition device for acquiring a        state of the electrical discharge between the discharge        electrode and the wire;    -   a second means for opening and closing a plurality of clampers,        respectively, for gripping the wire; and    -   a computer for controlling wire bonding between a first bonding        point and a second bonding point, and this computer includes        -   a third means for electrically detecting whether the            electrical discharge of the ball formation device is normal            or not by processing electrical discharge state signals            acquired by the electrical discharge state acquisition            device during the electrical discharge of the ball formation            device and indicative of electrical discharge state between            the discharge electrode and the wire,        -   a fourth means for detecting a shape of a tip end of the            wire by processing elevation images of the wire in the            vicinity of the tip end of the capillary acquired by the            first means via the light path device,        -   a fifth means for, when an electrical discharge anomaly is            detected by the third means and a condition of the wire at            the tip end of the capillary detected by the fourth means is            not a prescribed condition, paying out the wire at the tip            end of the capillary until the wire at the tip end of the            capillary attains a prescribed condition, by an up-and-down            movement of the capillary caused by the second means and            moving mechanism, based on a condition of the wire at the            tip end of the capillary detected by the fourth means, and        -   a sixth means for, when a condition of the wire at the tip            end of the capillary detected by the fourth means is a            prescribed condition after an electrical discharge anomaly            is detected by the third means, reforming the tip end of the            wire into a ball of a prescribed shape by the ball formation            device based on the tip end shape of the wire detected by            the fourth means.

The object of the present invention can be accomplished by a recordmedium storing a bonding control program for a wire bonding apparatusthat bonds a wire between a first bonding point and a second bodingpoint, wherein the wire bonding apparatus includes

-   -   a moving mechanism for moving, in XYZ directions, a capillary        having a wire inserted therethrough and executing bonding on a        work,    -   an electrical conduction state acquisition device for detecting        an electrical conduction state by allowing an electric current        to flow from the wire to the work,    -   a light path device for conducting an elevation image of a        vicinity of a tip end of the capillary to an imaging device,    -   a ball formation device for forming a tip end of the wire into a        ball of a prescribed shape, and    -   a computer for controlling the wire bonding apparatus; and

the record medium storing a bonding control program is executed by thecomputer and includes

-   -   an electrical non-bonding detection program for electrically        detecting non-bonding between the first bonding point and the        wire by processing electrical conduction state signals acquired        by the electrical conduction state acquisition device and        indicative of electrical conduction state between a first        bonding point and a wire;    -   an optical non-bonding detection program for optically detecting        non-bonding between a first bonding point and a wire by        processing plane images acquired by the imaging device;    -   an optical shape detection program for detecting a shape of a        tip end of the wire by processing elevation images of the wire        in the vicinity of the tip end of the capillary acquired by the        imaging device via the light path device; and    -   a non-bonding recovery program for, when a non-bonding detection        is output by the electrical non-bonding detection program and a        non-bonding detection is output by the optical non-bonding        detection program, reforming a ball of a prescribed shape at the        tip end of the wire by the ball formation device based on the        tip end shape of the wire output by the optical shape detection        program, and executing rebonding at the first bonding point.

The above-described wire bonding apparatus which is controlled by theabove-described bonding control program can further include a clamperoperating device for opening and closing a plurality of clampers,respectively, for gripping the wire; and the above-described recordmedium storing bonding control program can further include a tailre-payout program for, when a non-bonding detection is output by theelectrical non-bonding detection program and a non-bonding detection isoutput by the optical non-bonding detection program and an output ismade by the optical shape detection program to the effect that acondition of the wire at the tip end of the capillary is not aprescribed condition, paying out the wire at the tip end of thecapillary until the wire at the tip end of the capillary attains aprescribed condition, by an up-and-down movement of the capillary causedby the clamper operating device and moving mechanism, based on acondition of the wire at the tip end of the capillary output by theoptical shape detection program.

The object of the present invention can be accomplished by a recordmedium storing a bonding control program for a wire bonding apparatusthat bonds a wire between a first bonding point and a second bodingpoint, wherein the wire bonding apparatus includes

-   -   a moving mechanism for moving, in XYZ directions, a capillary        having a wire inserted therethrough and executing bonding on a        work,    -   an electrical conduction state acquisition device for detecting        an electrical conduction state by allowing an electric current        to flow from the wire to the work,    -   an imaging device for taking an image of the work,    -   a light path device for conducting an elevation image of a        vicinity of a tip end of the capillary to the imaging device,    -   a ball formation device for forming a tip end of the wire into a        ball of a prescribed shape,    -   a clamper operating device for opening and closing a plurality        of clampers, respectively, for gripping the wire, and    -   a computer for controlling the wire bonding apparatus; and

the record medium storing a bonding control program is characterized inthat it is executed by the computer and includes

-   -   an electrical no-tail detection program for detecting no-tail,        in which a tail of the wire fails to have a prescribed length,        by processing electrical conduction state signals acquired by        the electrical conduction state acquisition device, after        bonding on a second bonding point but prior to wire cutting, and        indicative of electrical conduction state between the second        bonding point and the wire;    -   an optical shape detection program for detecting a shape of a        tip end of the wire by processing elevation images of the wire        in the vicinity of the tip end of the capillary acquired by the        imaging device via the light path device;    -   a tail re-payout program for, when a no-tail detection is output        by the electrical no-tail detection program and an output is        made by the optical shape detection program to the effect that a        condition of the wire at the tip end of the capillary is not a        prescribed condition, paying out the wire at the tip end of the        capillary until the wire at the tip end of the capillary attains        a prescribed condition, by an up-and-down movement of the        capillary caused by the clamper operating device and moving        mechanism, based on a condition of the wire at the tip end of        the capillary output by the optical shape detection program; and    -   a no-tail recovery program for reforming the tip end of the wire        into a ball of a prescribed shape by the ball formation device        based on the tip end shape of the wire output by the optical        shape detection program.

The object of the present invention can be accomplished by a recordmedium storing a bonding control program for a wire bonding apparatusthat bonds a wire between a first bonding point and a second bodingpoint, wherein the wire bonding apparatus includes

-   -   a moving mechanism for moving, in XYZ directions, a capillary        having a wire inserted therethrough and executing bonding on a        work,    -   an imaging device for taking an image of the work,    -   a light path device for conducting an elevation image of a        vicinity of a tip end of the capillary to the imaging device,    -   a ball formation device for forming a tip end of the wire into a        ball of a prescribed shape by an electrical discharge between a        discharge electrode and the wire,    -   an electrical discharge state acquisition device for acquiring a        state of the electrical discharge between the discharge        electrode and the wire,    -   a clamper operating device for opening and closing a plurality        of clampers, respectively, for gripping the wire, and    -   a computer for controlling the wire bonding apparatus; and

the record medium storing a bonding control program is characterized inthat it is executed by the computer and includes

-   -   a discharge anomaly electrical detection program for        electrically detecting whether the electrical discharge of the        ball formation device is normal or not by processing electrical        discharge state signals acquired by the electrical discharge        state acquisition device during the electrical discharge of the        ball formation device and indicative of electrical discharge        state between the discharge electrode and the wire,    -   an optical shape detection program for detecting a shape of a        tip end of the wire by processing elevation images of the wire        in the vicinity of the tip end of the capillary acquired by the        imaging device via light path device,    -   a tail re-payout program for, when an electrical discharge        anomaly is output by the discharge anomaly electrical detection        program and an output is made by the optical shape detection        program to the effect that a condition of the wire at the tip        end of the capillary is not a prescribed condition, paying out        the wire at the tip end of the capillary until the wire at the        tip end of the capillary attains a prescribed condition, by an        up-and-down movement of the capillary caused by the clamper        operating device and moving mechanism, based on a condition of        the wire at the tip end of the capillary output by the optical        shape detection program, and    -   a discharge anomaly recovery program for, when an electrical        discharge anomaly is output by the discharge anomaly electrical        detection program and an output is made by the optical shape        detection program to the effect that a condition of the wire at        the tip end of the capillary is a prescribed condition,        reforming the tip end of the wire into a ball of a prescribed        shape by the ball formation device based on the tip end shape of        the wire output by the optical shape detection program.

The object of the present invention can be accomplished by a bondingmethod for a bonding apparatus that bonds a wire between a first bondingpoint and a second bonding point, and this method is characterized inthat it includes the steps of

-   -   preparing        -   a moving mechanism for moving, in XYZ directions, a            capillary having a wire inserted therethrough and executing            bonding on a work,        -   an electrical conduction state acquisition device for            detecting an electrical conduction state by allowing an            electric current to flow from the wire to the work,        -   an imaging device for taking an image of the work,        -   a light path device for conducting an elevation image of a            vicinity of a tip end of the capillary to the imaging            device,        -   a ball formation device for forming the tip end of the wire            into a ball of a prescribed shape, and        -   a computer for controlling the bonding apparatus;    -   an electrical non-bonding detection step for electrically        detecting non-bonding between the first bonding point and the        wire by processing electrical conduction state signals acquired        by the electrical conduction state acquisition device and        indicative of electrical conduction state between the first        bonding point and the wire;    -   an optical non-bonding detection step for optically detecting        non-bonding between the first bonding point and the wire by        processing plane images acquired by the imaging device;    -   an optical shape detection step for detecting a shape of a tip        end of the wire by processing elevation images of the wire in        the vicinity of the tip end of the capillary acquired by the        imaging device via the light path device; and    -   a non-bonding recovery step for, when non-bonding is detected in        the electrical non-bonding detection step and non-bonding is        detected in the optical non-bonding detection step, reforming        the tip end of the wire into a ball of a prescribed shape by the        ball formation device, based on the tip end shape of the wire        detected in the optical shape detection step, and executing        rebonding on the first bonding point.

The above-described wire bonding apparatus in which the above-describedbonding method is employed can further include a clamper operatingdevice for opening and closing a plurality of clampers, respectively,for gripping the wire; and the above-described bonding method canfurther include a tail re-payout step for, when non-bonding is detectedin the electrical non-bonding detection step and non-bonding is detectedin the optical non-bonding detection step and a condition of the wire atthe tip end of the capillary detected in the optical shape detectionstep is not a prescribed condition, paying out the wire at the tip endof the capillary until the wire at the tip end of the capillary attainsa prescribed condition by an up-and-down movement of the capillarycaused by the clamper operating device and moving mechanism based on acondition of the wire at the tip end of the capillary detected in theoptical shape detection step.

The object of the present invention can be accomplished by a bondingmethod for a bonding apparatus that bonds a wire between a first bondingpoint and a second bonding point, and this method is characterized inthat it includes the steps of

-   -   preparing        -   a moving mechanism for moving, in XYZ directions, a            capillary having a wire inserted therethrough and executing            bonding on a work,        -   an electrical conduction state acquisition device for            detecting an electrical conduction state by allowing an            electric current to flow from the wire to the work,        -   an imaging device for taking an image of the work,        -   a light path device for conducting an elevation image of a            vicinity of a tip end of the capillary to the imaging            device,        -   a ball formation device for forming the tip end of the wire            into a ball of a prescribed shape,        -   a clamper operating device for opening and closing a            plurality of clampers, respectively, for gripping the wire,            and        -   a bonding control computer for controlling the bonding            apparatus;    -   an electrical no-tail detection step for detecting no-tail in        which a tail of the wire fails to have a prescribed length by        processing electrical conduction state signals acquired by the        electrical conduction state acquisition device, after bonding to        the second bonding point but prior to wire cutting, and        indicative of electrical conduction state between the second        bonding point and the wire;    -   an optical shape detection step for detecting a shape of a tip        end of the wire by processing elevation images of the wire in        the vicinity of the tip end of the capillary acquired by the        imaging device via the light path device;    -   a tail re-payout step for, when a no-tail is detected in the        electrical no-tail detection step and a condition of the wire at        the tip end of the capillary detected in the optical shape        detection step is not a prescribed condition, paying out the        wire at the tip end of the capillary until the wire at the tip        end of the capillary attains a prescribed condition, by an        up-and-down movement of the capillary caused by the clamper        operating device and moving mechanism, based on a condition of        the wire at the tip end of the capillary detected in the optical        shape detection step; and    -   a no-tail recovery step for reforming the tip end of the wire        into a ball of a prescribed shape by the ball formation device        based on the tip end shape of the wire detected in the optical        shape detection step.

The object of the present invention can be accomplished by a bondingmethod for a bonding apparatus that bonds a wire between a first bondingpoint and a second bonding point, and this method is characterized inthat it includes the steps of

-   -   preparing        -   a moving mechanism for moving, in XYZ directions, a            capillary having a wire inserted therethrough and executing            bonding on a work,        -   an imaging device for taking an image of the work,        -   a light path device for conducting an elevation image of a            vicinity of a tip end of the capillary to the imaging            device,        -   a ball formation device for forming a tip end of the wire            into a ball of a prescribed shape by an electrical discharge            between a discharge electrode and the wire,        -   an electrical discharge state acquisition device for            acquiring a state of the electrical discharge between the            discharge electrode and the wire, and        -   a clamper operating device for opening and closing a            plurality of clampers, respectively, for gripping the wire;    -   a discharge anomaly electrical detection step for electrically        detecting whether the electrical discharge of the ball formation        device is normal or not by processing electrical discharge state        signals acquired by the electrical discharge state acquisition        device during the electrical discharge of the ball formation        device and indicative of electrical discharge state between the        discharge electrode and the wire;    -   an optical shape detection step for detecting a shape of a tip        end of the wire by processing elevation images of the wire in        the vicinity of the tip end of the capillary acquired by the        imaging device via the light path device;    -   a tail re-payout step for, when an electrical discharge anomaly        is detected in the discharge anomaly electrical detection step        and a condition of the wire at the tip end of the capillary        detected in the optical shape detection step is not a prescribed        condition, paying out the wire at the tip end of the capillary        until the wire at the tip end of the capillary attains a        prescribed condition, by an up-and-down movement of the        capillary caused by the clamper operating device and moving        mechanism, based on a condition of the wire at the tip end of        the capillary detected in the optical shape detection step; and    -   a discharge anomaly recovery step for, when an electrical        discharge anomaly is detected in the discharge anomaly        electrical detection step and a condition of the wire at the tip        end of the capillary detected in the optical shape detection        step is a prescribed condition, reforming the tip end of the        wire into a ball of a prescribed shape by the ball formation        device based on the tip end shape of the wire detected in the        optical shape detection step.

With the wire bonding apparatus, the bonding control program, and thebonding method of the present invention, when a pad (first bondingpoint) non-bonding, lead (second bonding point) non-bonding, no-tail, ordischarge error or the like occurs, recovery processing is executedwithout stopping the wire bonding apparatus, and bonding is continued.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic view of the control system of the wire bondingapparatus of the present invention;

FIG. 2 is a flowchart of the overall recovery process in the presentinvention;

FIG. 3 is a flowchart of the pad non-bonding recovery process in thepresent invention;

FIG. 4 is a flowchart of the no-tail recovery process in the presentinvention;

FIG. 5 is a flowchart of the tail re-payout process in the presentinvention;

FIG. 6 shows the steps (a) to (k) of the pad non-bonding recoveryprocess in the present invention;

FIG. 7 shows the steps (a) to (l) of the pad non-bonding recoveryprocess including a discharge anomaly recovery process in the presentinvention;

FIG. 8 shows the steps (a) to (g) of the no-tail recovery process in thepresent invention;

FIG. 9 shows the steps (a) to (g) of the tail re-payout process in thepresent invention;

FIGS. 10A and 10B show plane images of a pad unit acquired by the planeimage acquisition device in the present invention;

FIGS. 11A through 11E show the elevation images of the vicinity of thetip end of a wire;

FIG. 12 is a schematic view of a conventional wire bonding apparatus;

FIG. 13 is a flowchart of the overall wire bonding process in theconventional wire bonding apparatus;

FIG. 14 shows the steps (a) to (f) of the wire bonding actions in theconventional wire bonding apparatus; and

FIG. 15 is a top view of a semiconductor chip wire-bonded to a leadframe.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described below. In thefollowing descriptions, the same symbols are used for the portions thatare the same as those described above relative to the conventional art,and no further description thereof will be given.

First Embodiment

The wire bonding apparatus 10 of the First Embodiment of the presentinvention is shown in FIG. 1. The wire bonding apparatus 10 comprises,instead of the position detection camera 128 of the conventional wirebonding apparatus 100, an imaging device 28 that is capable of not onlydetecting a position but also imaging a work; and the wire bondingapparatus 10 further includes two clampers, namely a first clamper 17 aand a second clamper 17 b, that are opened and closed, respectively, bya clamper operating device 27. This clamper operating device isdisclosed in the allowed claims of U.S. Pat. No. 5,323,948 (Thedisclosure of the claims of this patent is incorporated by reference).The clamper operating device operates a pair of (two) clamping arms ofeach one of the first and second clampers, each holding a bonding wirebetween the clamping arms; and at least one of the clamping arms isoperated (opened and closed) by electric strain effect or magneticstrain effect of a piezoelectric element. Such at least one clamping armcan be operated by a solenoid, and it can be further operated by alinear motor. The first clamper 17 a is movable in the Z directiontogether with the capillary 16, while the second clamper 17 b is fixedto the bonding head 19.

The wire bonding apparatus 10 additionally includes a light path device24 for conducting a plane image of the vicinity of the tip end of thecapillary 16 to the imaging device 28 and an electrical discharge stateacquisition device 29 for acquiring the state of electrical dischargesbetween a discharge electrode and the wire 12.

The imaging device 28 is connected to the imaging device interface 40,the clamper operating device 27 is connected to the clamper open/closeinterface 48, the electrical discharge state acquisition device 29 isconnected to the electrical discharge state interface 50, and theinterfaces are respectively connected via the data bus 32 to the controlsection 30. The first clamper 17 a is moved in Z direction together withthe capillary 16, and the second clamper 17 b is secured to the bondinghead 19. Furthermore, the computer 31 includes an imaging deviceinterface 40, a clamper open/close interface 48, an electricalconduction state acquisition device interface 42, a moving mechanisminterface 44, a ball formation device interface 46, an electricaldischarge state acquiring interface 50, a memory unit 34, a data bus 32and a control section 30. The memory unit 34 of the present inventionincludes both internal memory section and external memory section, inwhich the internal memory section has a function to, among others,store, read-out and write-in the control data, and the external memorysection functions as a computer readable medium.

The wire bonding apparatus 10 structured as described above iscontrolled by the computer 31 and performs bonding and recovery actionsor processes, when non-bonding of a pad 3 (first bonding point) occurs,with the steps described below:

-   -   (1) Bonding to the pad 3 (first bonding point), and non-bonding        detection, are performed by the same methods and steps as those        described relative to the conventional art (steps S101 to S105        in FIG. 2, steps (a) to (c) in FIG. 6).    -   (2) Even when non-bonding of the pad 3 (first bonding point) is        detected by the electrical non-bonding detection program 71 that        processes a signal from the electrical conduction state        acquisition device 22 by the control section 30 of the computer        31, the capillary 16 continues as before to move to the lead 4        (second bonding point) and performs bonding at the lead 4        (second bonding point) (step S106 in FIG. 2, step (d) in FIG.        6). However, no acquisition of the electrical conduction state        is made in order to detect a no-tail condition or lead        non-bonding condition at the lead 4 (second bonding point). More        specifically, the electrical conduction state acquisition device        22 involves resistance or impedance (not shown) therein, and the        electrical non-bonding detection program 71 causes the control        section 30 to compare A/D-converted data with no-bonding        reference data stored in advance in the memory unit 34; and when        the A/D-converted data is out of the range of the non-bonding        reference data, then the electrical non-bonding detection        program 71 determines the non-bonding. The above-described        A/D-converted data is obtained by the electrical conduction        state acquisition device 22 that applies direct voltage or        alternate current from the wire to the work, for detecting        non-bonding, and converts the difference in the electrical        potentials generated, relatively, in the resistance or impedance        and then A/D-converts the difference in the electrical        potentials into an A/D-converted data via the electrical        conduction state acquisition device interface 42.    -   (3) After bonding to the lead 4 (second bonding point), the        capillary 16 is made to ascend, and the tail 8 of the wire (or        the tail wire 8) is extended; and after which the first clamper        17 a is closed and made to ascend together with the capillary        16, and the wire 12 is cut (steps S106 to S108 in FIG. 2,        steps (e) to (f) in FIG. 6). By this bonding action to the lead        4 (second bonding point), a tail wire 8 is made in which ball        formation at the tip end of the capillary 16 is possible.    -   (4) When non-bonding of the pad 3 (first bonding point) is        detected by executing the electrical non-bonding detection        program 71, the control section 30 of the computer 31 issues a        command to execute the non-bonding recovery program 74 for pad.        By that command, a process of pad non-bonding recovery S109 by        the non-bonding recovery program 74 for pad is started.    -   (5) When the process S109 by the non-bonding recovery program 74        for pad is started, the computer 31 moves the imaging device 28,        which is comprised of a camera including digital image sensors,        such as CCD (charge-coupled device) cameras, CMOS (complementary        metal-oxide semiconductor) cameras, etc., by the moving        mechanism 18, to a position at which the pad 3 (first bonding        point) enters the visual field 60 thereof (i.e. of the imaging        device 28) (step S202 in FIG. 3). Then, a plane image of the        vicinity of the pad 3 (first bonding point) where the        non-bonding was detected is acquired (step S203 in FIG. 3,        step (g) in FIG. 6). The acquired plane image is input to the        control section 30 via the imaging device interface 40, and that        image is analyzed (step S204 in FIG. 3).

Examples of acquired plane images are shown in FIGS. 10A and 10B. FIG.10A shows the condition where bonding has been done properly, while FIG.10B shows non-bonding. In both FIGS. 10A and 10B, bonding is done frombelow in the visual field 60 upward, with the lower pad being a padwhere bonding has been already finished normally, the middle pad 3 beingthe pad 3 (first bonding point) where bonding is being done, and theuppermost pad being an unbonded pad. In FIG. 10A, a first bond 6(pressure-bonded ball) formed by pressure bonding on the middle pad canbe seen, but in FIG. 10B the first bond (pressure-bonded ball) cannot beseen on the pad 3. By processing such a plane image by the opticalnon-bonding detection program of the computer 31, it is possible todetect whether or not the first bond 6 (pressure-bonded ball) actuallyhas been formed and bonding has been performed. Non-bonding detectioncan be done by determining whether the first bond 6 (pressure-bondedball) is there or not by the optical non-bonding detection program ofthe computer 31, or non-bonding detection processing can be performed byfirst storing shape data on the first bond (pressure-bonded ball) in thememory unit 34, and then comparing that data by the optical non-bondingdetection program 72. The optical non-bonding detection program 72, morespecifically, causes the control section 30 to compare the data in whichthe image of the pad 3 obtained from the imaging device 28 is convertedinto image measured values via the imaging device interface 40 and thereference data on the pad 3 stored in advance in the memory unit 34; andwhen the data converted into the image measured values is unmatched withthe reference data, the optical non-bonding detection program 72determines non-bonding of the pad 3.

-   -   (6) When it is determined by executing the optical non-bonding        detection program 72 that the pad 3 (first bonding point) is        non-bonding, the computer 31 moves the capillary 16, by the        moving mechanism 18, to the discharge position for redoing ball        formation by electrical discharge (step S206 in FIG. 3, step (h)        in FIG. 6).    -   (7) Once moved to the discharge position, an electrical        discharge is effected between the tail wire 8 and the discharge        electrode of a ball formation device 26, so that the tip end of        the tail wire 8 is formed into a ball shape. The shape of the        ball formed by electrical discharge is determined by the amount        of electrical charge applied to the tail wire 8 by the        electrical discharge (or discharge). The charge amount can be        found as the integral of the discharge current, for example, and        for detecting whether or not electrical discharge has been        effected properly when that value becomes a prescribed value. In        addition, the same results can be obtained by way of detecting        discharge voltage by a voltage divider. The electrical discharge        state acquisition device 29 acquires at least one of or both of        electric current conditions at the time of electrical discharge        such as discharge current and electric voltage conditions at the        time of electrical discharge such as discharge voltage as        described above. Those acquired data are input in the control        section 30 by the electrical discharge state interface 50 and        subjected to comparison processing with the data in the memory        unit 34 by executing the discharge anomaly electrical detection        program 78; and then a determination is made as to whether a        discharge anomaly is occurred or not (steps S207 to S209 in FIG.        3). The discharge anomaly electrical detection program 78        executes, for a predetermined period of time, sampling of the        discharge voltage values and discharge current values from the        discharge circuit (not shown) installed in the ball formation        device 26. The sampled discharge voltage values and discharge        current values are A/D-converted into measured discharge values        via the discharge state interface 50 from the electrical        discharge state acquisition device 29 and read-in by the control        section 30. Then, the discharge anomaly electrical detection        program 78 causes the control section 30 to compare the measured        discharge voltage data and measured discharge current data with        the reference discharge voltage data and reference discharge        current data, respectively; and when the measured discharge        voltage data and measured discharge current data are,        respectively, out of the range of the reference discharge        voltage data and reference discharge current data, then the        discharge anomaly electrical detection program 78 determines the        discharge anomaly.    -   (8) When no discharge anomaly is detected by the discharge        anomaly electrical detection program, and it is determined that        electrical discharge has been normally effected, then the        computer 31 moves the tip end of the capillary 16, by the moving        mechanism 18, to an elevation image acquisition position where        the light path device 24 is provided (step S210 in FIG. 3). A        reference member 25 is attached to a base 23 at an elevation        image acquisition position.    -   (9) At the elevation image acquisition position, the tip end of        the capillary 16 is illuminated, together with the reference        member 25, by a light emitter 21 (see step (i) in FIG. 6) such        as a light-emitting diode, from the side surface of the        capillary 16 to form an elevation image. The elevation image        formed is conducted to the imaging device 28 by the light path        device 24 made of a lens 24 a and prism 24 b. The imaging device        28 acquires this elevation image of the tip end of the capillary        16 and inputs it to the control section 30 from the imaging        device interface 40 (step S211 in FIG. 3, step (i) in FIG. 6).        The input elevation image is processed by executing the optical        shape detection program 73 of the computer 31; and a        determination is made as to whether or not the diameter of the        ball 5 formed is a prescribed diameter (step S212 in FIG. 3).        When the ball 5 is formed, the acquired elevation image includes        the capillary 16, ball 5, tail wire 8, and reference member 25        contained in the visual field 62, as shown in FIGS. 11D and 11E.        It can be possible that the control section 30, based on the        results of a calibration of the relationship between the number        of pixels found in advance and the length of the object(s) in        the visual field, finds the ball diameter from the number of        pixels in the ball 5 portion of the image, or provision can be        made so that the relative length with the reference numeral        captured in the visual field 62 together is found, and the ball        diameter is found from that relationship. Then, the ball        diameter acquired by executing the optical shape detection        program 73 is compared with prescribed standard range data        stored in the memory unit 34, and a determination is made as to        whether or not the ball diameter is within the prescribed        standard range (step S212 in FIG. 3, step (i) in FIG. 6). The        optical shape detection program 73 causes the control section 30        to compare the data of the elevation image of the wire tail 8        obtained from the imaging device 28 and converted into image        measured values via the imaging device interface 40 with the        elevation image reference data stored in advance in the memory        unit 34; and when the data converted into image measured values        is unmatched with the elevation image reference data, then        optical shape detection program 73 determines the non-bonding.    -   (10) When the shape of the ball 5 detected by executing the        optical shape detection program 73 is within an allowable range,        the non-bonding recovery program 74 for pad is ended (step S214        in FIG. 3).    -   (11) When the pad non-bonding recovery routine S109 ends, the        computer 31 again moves the position of the capillary 16, by the        moving mechanism 18, to the pad 3 (first bonding point) (to step        S102 from step S109 in FIG. 2, step (j) in FIG. 6).    -   (12) Then, bonding is performed again at the pad 3 (first        bonding point) (step S102 in FIG. 2, step (k) in FIG. 6).    -   (13) When the shape of the ball is not a prescribed shape, it is        determined that a pad non-bonding recovery failure on the pad        has occurred, and error stop processing is performed (step S213        in FIG. 3).

As seen from the above, in the wire bonding apparatus capable ofexecuting process by the non-bonding recovery program 74 for padaccording to the First Embodiment of the present invention, after anon-bonding of pad is detected by executing the electrical non-bondingdetection program 71 based upon the electrical conduction state, thecondition of the non-bonding is further detected by the opticalnon-bonding detection program 72 and determination thereof is made, andthen a non-bonding of pad is deemed to have occurred when thenon-bonding is detected by both detection means. Accordingly, stoppagesthat result from erroneous non-bonding detection become significantlyfewer in the present invention compared to the conventional wire bondingapparatuses in which non-bonding is determined and stop processing iseffected only from the results of the electrical non-bonding detectionmeans; and in the present invention, the operating ratio can be improvedremarkably.

In addition, in the First Embodiment, when pad non-bonding is detectedby executing the electrical non-bonding detection program 71 based onthe electrical conduction state and by executing the optical non-bondingdetection program 72 based on plane images, a ball is formed byeffecting electrical discharge again; and the shape of the ball isdetected by the optical shape detection program 73, and a determinationthereof is made; and then if a prescribed shape has been realized, theprocess returns to the pad 3 (first bonding point), redoing isperformed, and bonding action is continued. Thus, the process executedby the non-bonding recovery program 74 for pad is executed assuredly;and such a benefit is realized that bonding action can be continuedwithout an operator having, due to the occurrence of pad non-bonding, totemporarily stop the wire bonding apparatus and inspect the situation.In particular, since dozens of wire bonding apparatuses are generallyoperated simultaneously, the fact that the bonding action can becontinued without stopping the wire bonding apparatuses by recoveryprocessing provides a marked benefit in bringing about vastly improvedequipment operating efficiencies.

Second Embodiment

In the process by the non-bonding recovery program 74 for pad of theabove-described First Embodiment, after the bonding to lead 4 (secondbonding point), the tail wire 8 is formed well; and no discharge anomalyoccurs with the ball formation device 26. However, when a non-bondingerror occurs at the pad 3 (first bonding point) in the wire bondingapparatus 10, there are cases that the ball is not formed into aprescribed shape by re-discharge because the shape of the tip end of thewire after non-bonding is also anomalous. In view of this, the SecondEmbodiment of the present invention is a processing executed by thenon-bonding recovery program 74 for pad that includes the processingexecuted by the discharge anomaly recovery program 79. In thedescription below, the same symbols are used for the steps that are thesame as for the processing executed by the non-bonding recovery program74 for pad described above, and no further description will be given tothem.

-   -   (1) In like manner as in the above-described process executed by        the non-bonding recovery program 74 for pad, after non-bonding        is detected for the pad 3 (first bonding point) by executing the        electrical non-bonding detection program 71 by a signal from the        electrical conduction state acquisition device 22 when bonding        is made to the pad 3 (first bonding point) (S101 to S105 to S108        in FIG. 2), the step advances to the process (S109) executed by        the non-bonding recovery program 74 for pad; and, when        non-bonding for the pad 3 (first bonding point) is detected by        executing the optical non-bonding detection program 72, in like        manner as in the above-described process executed by the        non-bonding recovery program 74 for pad, the capillary 16 is        moved to the discharge position, and the ball 5 is reformed by        the ball formation device 26 (steps S201 to S207 in FIG. 3,        steps (a) to (h) in FIG. 7).    -   (2) However, when a good tail wire 8 is not formed, or the        length of the tail wire 8 is shorter than the prescribed length        (steps (e) and (f) in FIG. 7) as a result of the processing        step(s) of bonding to the lead 4 (second bonding point), the        distance between the electrode of the ball formation device 26        and the tail wire 8 is too long, and prescribed electrical        discharge cannot be effected, and thus the ball will not be        formed well. Electrical discharge anomalies can be detected by        executing the discharge anomaly electrical detection program        that fetches data from the electrical discharge state        acquisition device 29 by the electrical discharge state        interface 50 into the control section 30 and process those data.    -   (3) When a discharge anomaly is detected by executing the        discharge anomaly electrical detection program, the computer 31        moves the tip end of the capillary 16, by the moving mechanism        18, to the elevation image acquisition position where the light        path device 24 is provided (step S215 in FIG. 3).    -   (4) At the elevation image acquisition position, in like        processing as in the above-described non-bonding recovery        program 74 for pad, an elevation image of the tip end of the        capillary 16 is captured, and the imaging device 28 inputs that        elevation image of the tip end of the capillary 16 into the        control section 30 via the imaging device interface 40 (step        S216 in FIG. 3, step (i) in FIG. 7). The input elevation image        is processed by executing the optical shape detection program 73        of the computer 31, and the conditions of the tail wire at the        tip end of the capillary 16, such as length, inclination, and        bend, are acquired (step S216 in FIG. 3). The acquired elevation        image includes the capillary 16, tail wire 8, and reference        member 25 in the visual field 62, as shown in FIGS. 11A to 11C.        The computer 31 finds the length and inclination of and the        degree of bend in the tail wire 8, by executing the optical        shape detection program. Then, the shape of the tail wire 8        acquired is compared with reference data stored in the memory        unit 34 and; when that is not a prescribed shape, then a        processing S218 for paying out the wire 12 in the tip end of the        capillary 16 is executed by the tail re-payout program 75 (steps        S217 and S218 in FIG. 3, FIG. 7( i)).    -   (5) The processing S218 executed by the tail re-payout program        75, as shown in FIG. 5 and FIG. 9, is conducted by the opening        and closing action of the two (first and second) clampers 17 a        and 17 b, and the up-and-down movement of the capillary 16 and        the first clamper 17 a. The opening and closing actions of the        clampers are effected by the input of signals from the control        section 30 to the clamper operating device 27 via the clamper        open/close interface 48. The processing S218 executed by the        tail re-payout program 75 will be described below.        -   (a) Verification is made that both the first clamper 17 a            and the second clamper 17 b are in a closed condition (step            S402 in FIG. 5, FIG. 9( a)).        -   (b) The second clamper 17 b is opened (step S403 in FIG. 5,            step (b) in FIG. 9).        -   (c) The wire 12, while being clamped by the first clamper 17            a, is made to descend together with the capillary, and            stopped at a prescribed position (step S404 in FIG. 5,            steps (c) to (d) in FIG. 9). By this action, the first            clamper 17 a pulls out the wire 12 wound on the spool 11.        -   (d) The second clamper 17 b is closed, and the first clamper            17 a is opened (S406 in FIG. 5, step (e) in FIG. 9).        -   (e) In this condition, the capillary 16 and the first            clamper 17 a are made to ascend. When the ascending is done,            since the wire 12 is secured by the second clamper 17 b, the            wire comes jumping out at the tip end of the capillary 16            (step S407 in FIG. 5, step (f) FIG. 9).        -   (f) Once the capillary 16 and the first clamper 17 a have            returned to their prescribed positions, the first clamper 17            a is closed, and verification is made that the first and            second clampers 17 a and 17 b are closed (steps S409 and            S410 in FIG. 5, step (g) in FIG. 9). The processing S218            executed by tail re-payout program 75 does not pay out the            wire one time so that it attains the prescribed length, but            rather repeatedly, some number of times, pays out a little            at a time. Every time a wire pay-out is made, the wire            length paid out at the tip end of the capillary is detected            and measured by the optical shape detection program 73; and,            once it is determined that the prescribed length and shape            have been attained, then the processing S218 executed by the            tail re-payout program 75 is ended (steps S218 to S220 in            FIG. 3).    -   (6) When the tail wire 8 attains the prescribed condition by the        processing S218 executed by the tail re-payout program 75, the        computer 31 moves the capillary 16, by the moving mechanism 18,        to the discharge position (steps S220 to S206 in FIG. 3,        step (j) in FIG. 7).    -   (7) Once the movement to the discharge position is made, as in        the earlier electrical discharge step, electrical discharge is        effected between the discharge electrode of the ball formation        device 26 and the tail wire 8, and, as a result, the tip end of        the tail wire 8 is formed into a ball shape. When the electrical        discharge is effected well, and no discharge anomaly is detected        by executing the discharge anomaly electrical detection program        78, then the computer 31 moves the imaging device 28, by the        moving mechanism 18, to the elevation image acquisition position        and acquires an elevation image of the ball 5, and whether or        not the ball shape is the prescribed shape is detected by        executing the optical shape detection program 73 (steps S209 to        S212 in FIG. 3, steps (j) and (k) in FIG. 7).    -   (8) When the prescribed ball shape is attained, the processing        executed by the non-bonding recovery program 74 for pad        containing the processing executed by the discharge anomaly        recovery program 79 ends (step S214 in FIG. 3).    -   (9) When the processing executed by the non-bonding recovery        program 74 for pad ends, the computer 31 again moves the        position of the capillary 16, by the moving mechanism 18, to the        pad 3 (first bonding point) (steps S109 to S102 in FIG. 2,        step (l) in FIG. 7).    -   (10) Then, bonding is performed again at the pad 3 (first        bonding point) (step S102 in FIG. 2, step (b) in FIG. 7).    -   (11) When the shape of the ball is not a prescribed shape, it is        determined that failure of non-bonding recovery for pad has        occurred, and error stop processing is performed (step S213 in        FIG. 3). At that time, the ball shape is determined, and, until        the ball is formed into the prescribed shape, provision can be        made so that tail re-payout program 75 is executed again while        verifying the shape by executing the optical shape detection        program 73, effecting re-discharge and taking the recovery        cycle, or, alternatively, error stop processing can be done        after executing such processing some number of times.

As seen from the above, in the Second Embodiment of the presentinvention, even when the prescribed ball is not formed due to adischarge anomaly during the processing executed by the non-bondingrecovery program 74 for pad, bonding actions can be continued byperforming the processing executed by the discharge anomaly recoveryprogram 79 which is done by detecting the tail wire with an execution ofthe optical shape detection program 73 that determines the condition ofthe tail wire based on the elevation image thereof, by performing theprocess executed by the tail re-payout program 75 so that a prescribedball can be formed, and then by executing re-discharging to form a ball.From this fact, compared to the recovery processing that simply entailsonly the ball formation processing by re-discharge when a non-bondingsituation occurs as described earlier for the First Embodiment, tailre-payout and ball formation are conducted more appropriately in theSecond Embodiment, and thus the recovery process can be performed inmore diverse error conditions. As a consequence, bonding action can becontinued without stopping the bonding action even better than the FirstEmbodiment described earlier. In particular, this benefit is manifestedmore conspicuously when greater numbers of wire bonding apparatuses areoperated simultaneously.

Third Embodiment

Next, the Third Embodiment of the present invention that is for arecovery processing when a no-tail is detected at the lead 4 (secondbonding point) will be described. In the following description, the samesymbols are used for portions that are the same as those in thenon-bonding recovery processing for pad, recovery processing duringdischarge, and the processing executed by the tail re-payout program 75that are described above, and no further description will be giventhereto.

-   -   (1) As in the above-described processing executed by the        non-bonding recovery program 74 for pad, when no non-bonding is        detected for the pad 3 (first bonding point) by executing the        electrical non-bonding detection program by signals from the        electrical conduction state acquisition device 22 when bonding        to the pad 3 (first bonding point), bonding to the pad 3 (first        bonding point) is deemed to have been done well and bonding is        performed to the lead 4 (second bonding point). After bonding to        the lead 4 (second bonding point), electrical conduction state        signals are acquired by the electrical conduction state        acquisition device 22 during the ascent of the capillary 16        prior to wire cutting, and after the wire cutting action.        Thereafter, no-tail detection is made by processing S115        executed by the electrical no-tail detection program 76 from an        electrical conduction state signal prior to wire cutting. When a        no-tail is detected, the computer 31, as shown in FIG. 4,        outputs a command to start the processing S116 executed by the        no-tail recovery program 77 (steps S110 to S115 in FIG. 2,        steps (a) to (c) in FIG. 8). More specifically, the electrical        conduction state acquisition device 22 involves resistance or        impedance (not shown) therein, and the electrical no-tail        detection program 76 causes the control section 30 to compare        A/D-converted data with no-tail reference data stored in advance        in the memory unit 34; and when the A/D-converted data is out of        the range of the no-tail reference data, then the electrical        no-tail detection program 76 determines the no-tail. The        above-described A/D-converted data is obtained by the electrical        conduction state acquisition device 22 that applies direct        voltage or alternate current from the wire to the work        immediately before tail cutting, and converts the difference in        the electrical potentials generated, relatively, in the        resistance or impedance and then A/D-converts the difference in        the electrical potentials into an A/D-converted data via the        electrical conduction state acquisition device interface 42.    -   (2) When the processing S116 executed by the no-tail recovery        program 77 is started, the computer 31 moves the tip end of the        capillary 16, by the moving mechanism 18, to the elevation image        acquisition position where the light path device 24 is provided        and acquires an elevation image in the vicinity of the tip end        of the capillary (steps S302 and S303 in FIG. 4, step (d) in        FIG. 8).    -   (3) At the elevation image acquisition position, as with the        processing executed by the non-bonding recovery program 74 for        pad including the processing executed by the discharge anomaly        recovery program 79 described earlier, an elevation image of the        tip end of the capillary 16 is captured and input to the control        section 30 via the imaging device interface 40. The input        elevation image is processed in the control section 30, and the        conditions of the tail wire at the tip end of the capillary 16,        such as length, inclination, and bend, are acquired by executing        the optical shape detection program 73 (step S304 in FIG. 4).    -   (4) When the condition of the tail wire 8 acquired is not a        prescribed condition, then the processing S305 described earlier        is executed by the tail re-payout program 75, while detecting        the shape of the tail wire 8 by executing the optical shape        detection program 73, until the shape of the tail wire 8 attains        the prescribed shape (step S305 in FIG. 4, step (d) in FIG. 8).    -   (5) When the tail wire 8 attains the prescribed condition by the        processing S305 executed by the tail re-payout program 75, the        computer 31 moves the capillary 16, by the moving mechanism 18,        to the discharge position (step S306 in FIG. 4, step (e) in FIG.        8).    -   (6) Once the move to the discharge position is done, as in the        earlier electrical discharge step, electrical discharge is        effected and, as a result, the tip end of the tail wire 8 is        formed into a ball shape. When electrical discharge is performed        well, and no discharge anomaly is detected by executing the        discharge anomaly electrical detection program 78, then the        computer 31 effects movement of the imaging device 28 to the        elevation image acquisition position, by the moving mechanism        18, and acquires an elevation image of the ball 5; and whether        or not the ball shape has attained the prescribed shape is        detected by executing the optical shape detection program 73        (steps S309 to S312 in FIG. 4, step (f) in FIG. 8).    -   (7) When the prescribed ball shape is attained, the processing        executed by the no-tail recovery program 77 ends (step S314 in        FIG. 4).    -   (8) When the processing executed by the no-tail recovery program        77 ends, the bonding cycle ends (steps S116 to S119 in FIG. 2).    -   (9) The computer 31 moves the position of the capillary 16, by        the moving mechanism 18, to the next pad 3 (first bonding        point), and continues the next bonding action.    -   (10) When the shape of the ball has not attained the prescribed        shape, it is determined that a no-tail recovery failure has        occurred, and error stop processing is performed (step S313 in        FIG. 4). At this time, the ball shape is determined, and        provision can be made so that, until the ball is formed into a        prescribed shape, the processing executed by the tail re-payout        program 75 is done again while verifying the shape by executing        the optical shape detection program 73, effecting re-discharge        and go to the recovery cycle, or, alternatively, error stop        processing can be done after performing such processing executed        by such programs some number of times.

As seen from the above, with the Third Embodiment of the presentinvention, even when a no-tail error, in which the tail wire fails tohave a prescribed length, has occurred at the position of the lead 4(second bonding point), such no-tail error is detected by executing theoptical shape detection program that determines the condition of thattail wire by the elevation image, and a no-tail error recovery iseffected by performing the processing executed by the tail re-payoutprogram 75 and then re-discharging so that a prescribed ball formationbecomes possible, thus forming a ball, and then continuing the bondingactions. Accordingly, combined to the non-bonding recovery program forpad described earlier for the First and Second Embodiments, even morediverse error conditions can be coped with in the Third Embodiment, andbonding action can be continued without stopping the bonding action. Inparticular, this benefit is manifested more conspicuously when greaternumbers of wire bonding apparatuses are operated simultaneously.

1. A wire bonding apparatus comprising: a moving mechanism for moving,in XYZ directions, a capillary having a wire inserted therethrough andexecuting bonding on a work; a first means for taking an image of thework; a light path device for conducting an elevation image of avicinity of a tip end of the capillary to the first means; a ballformation device for forming a tip end of the wire into a ball of aprescribed shape by an electrical discharge between a dischargeelectrode and the wire; an electrical discharge state acquisition devicefor acquiring a state of the electrical discharge between the dischargeelectrode and the wire; a second means for opening and closing aplurality of clampers, respectively, for gripping the wire; and acomputer for controlling wire bonding between a first bonding point anda second bonding point, said computer including a third means forelectrically detecting whether the electrical discharge of the ballformation device is normal or not by processing electrical dischargestate signals acquired by the electrical discharge state acquisitiondevice during the electrical discharge of the ball formation device andindicative of electrical discharge state between the discharge electrodeand the wire, a fourth means for detecting a shape of a tip end of thewire by processing elevation images of the wire in the vicinity of thetip end of the capillary acquired by the first means via the light pathdevice, a fifth means for, when an electrical discharge anomaly isdetected by the third means and a condition of the wire at the tip endof the capillary detected by the fourth means is not a prescribedcondition, paying out the wire at the tip end of the capillary until thewire at the tip end of the capillary attains a prescribed condition, byan up-and-down movement of the capillary caused by the second means andmoving mechanism, based on a condition of the wire at the tip end of thecapillary detected by the fourth means, and a sixth means for, when acondition of the wire at the tip end of the capillary detected by thefourth means is a prescribed condition after an electrical dischargeanomaly is detected by the third means, reforming the tip end of thewire into a ball of a prescribed shape by the ball formation devicebased on the tip end shape of the wire detected by the fourth means. 2.A record medium storing a bonding control program for a wire bondingapparatus for bonding a wire between a first bonding point and a secondbonding point, said wire bonding apparatus including a moving mechanismfor moving, in XYZ directions, a capillary having a wire insertedtherethrough and executing bonding on a work, an imaging device fortaking an image of the work, a light path device for conducting anelevation image of a vicinity of a tip end of the capillary to theimaging device, a ball formation device for forming a tip end of thewire into a ball of a prescribed shape by an electrical dischargebetween a discharge electrode and the wire, an electrical dischargestate acquisition device for acquiring a state of the electricaldischarge between the discharge electrode and the wire, a clamperoperating device for opening and closing a plurality of clampers,respectively, for gripping the wire, and a computer for controlling saidwire bonding apparatus; said record medium storing a bonding controlprogram executed by said computer, comprising: a discharge anomalyelectrical detection program for electrically detecting whether theelectrical discharge of the ball formation device is normal or not byprocessing electrical discharge state signals acquired by the electricaldischarge state acquisition device during the electrical discharge ofthe ball formation device and indicative of electrical discharge statebetween the discharge electrode and the wire, an optical shape detectionprogram for detecting a shape of a tip end of the wire by processingelevation images of the wire in the vicinity of the tip end of thecapillary acquired by the imaging device via light path device, a tailre-payout program for, when an electrical discharge anomaly is output bythe discharge anomaly electrical detection program and an output is madeby the optical shape detection program to the effect that a condition ofthe wire at the tip end of the capillary is not a prescribed condition,paying out the wire at the tip end of the capillary until the wire atthe tip end of the capillary attains a prescribed condition, by anup-and-down movement of the capillary caused by the clamper operatingdevice and moving mechanism, based on a condition of the wire at the tipend of the capillary output by the optical shape detection program, anda discharge anomaly recovery program for, when an electrical dischargeanomaly is output by the discharge anomaly electrical detection programand an output is made by the optical shape detection program to theeffect that a condition of the wire at the tip end of the capillary is aprescribed condition, reforming the tip end of the wire into a ball of aprescribed shape by the ball formation device based on the tip end shapeof the wire output by the optical shape detection program.
 3. A bondingmethod for a bonding apparatus for bonding a wire between a firstbonding point and a second bonding point, comprising the steps of:preparing a moving mechanism for moving, in XYZ directions, a capillaryhaving a wire inserted therethrough and executing bonding on a work, animaging device for taking an image of the work, a light path device forconducting an elevation image of a vicinity of a tip end of thecapillary to the imaging device, a ball formation device for forming atip end of the wire into a ball of a prescribed shape by an electricaldischarge between a discharge electrode and the wire, an electricaldischarge state acquisition device for acquiring a state of theelectrical discharge between the discharge electrode and the wire, and aclamper operating device for opening and closing a plurality ofclampers, respectively, for gripping the wire; a discharge anomalyelectrical detection step for electrically detecting whether theelectrical discharge of the ball formation device is normal or not byprocessing electrical discharge state signals acquired by the electricaldischarge state acquisition device during the electrical discharge ofthe ball formation device and indicative of electrical discharge statebetween the discharge electrode and the wire; an optical shape detectionstep for detecting a shape of a tip end of the wire by processingelevation images of the wire in the vicinity of the tip end of thecapillary acquired by the imaging device via the light path device; atail re-payout step for, when an electrical discharge anomaly isdetected in the discharge anomaly electrical detection step and acondition of the wire at the tip end of the capillary detected in theoptical shape detection step is not a prescribed condition, paying outthe wire at the tip end of the capillary until the wire at the tip endof the capillary attains a prescribed condition, by an up-and-downmovement of the capillary caused by the clamper operating device andmoving mechanism, based on a condition of the wire at the tip end of thecapillary detected in the optical shape detection step; and a dischargeanomaly recovery step for, when an electrical discharge anomaly isdetected in the discharge anomaly electrical detection step and acondition of the wire at the tip end of the capillary detected in theoptical shape detection step is a prescribed condition, reforming thetip end of the wire into a ball of a prescribed shape by the ballformation device based on the tip end shape of the wire detected in theoptical shape detection step.